Electric-arc lamp



R. H. CUNNINGHAM.

ELECTRIC ARC LAMP.

(NoModel.)

Patented Aug. 13, 1895.

WITN ESSES NITED STATES PATE-NT OFFICE RICHARD H. CUNNINGHAM, OF RICHMOND, VIRGINIA.

ELECTRIC-ARC LAMP.

SPECIFICATION forming part of Letters Patent No. 544,529, dated August 13, 1895.

Application filed September 8,1894. Serial No. 522,448. (No model.)

To @ZZ whom, it may concern:

Be it known that I, RICHARD H. CUNNING- HAM, a citizen of the United States, residing at Richmond, in the county ot Henrico and State of Virginia, have invented certain new and useful Improvements in Electric-Arc Lamps, of which the following is a full, clear, and exact description.

This invention relates to electric-arc lamps, and has special reference to the class of lamps known as focusing.

The object of the invention is to produce a lamp of this character which shall give a perfectly steady radiant, maintained absolutely at a fixed point and especially adapted as a luminant in photomicrography and various forms of optical projection, theatrical illu mination, search-lights, light-houses, &c.

The lamp is operated upon the well-known differential principle; and the invention consists in the arrangement of the solenoids and their cores and the special devices connected therewith for transmitting motion to the lamp-electrodes.

The invention also consists of details of construction, which will be fully described and particularly pointed out in the claim.

In the accompanying drawings, Figure l represents a section of the lamp-casing and the regulating mechanism contained therein, the electrodes and holders being shown in side elevation. Fig. 2 is a detail of a differential winding-drum forming part ofthe regulating mechanism.

Referring to the drawings by letter, A represents the casing inclosing the regulating mechanism.

o and b, respectively, represent solenoids in series and in shunt with the lamp-electrodes. Through the central passage of solen oid c t extends a brass tube o, which projects some distance above and below the same and is guided by antifriction rollers c', xed to the head of the solenoid to insure free longis tudinal movement ot' the tube. Inside of the tube is al soft-iron core d. This core is conical in shape and its position within the tube may be adjusted and fixed by means of a setscrew d', (shown in dotted lines,) which passes through the tube and impinges against the core. The shunt-solenoid b is tted with a tube c, similar to the tube c, except that its length is about one-halt that of the tube c. It also contains a conical core f, which is adjustably connected with the tube by means of an extension f and thumb-screw working in a slotfs. This tube islikewise mounted upon antifriction-bearings. To the upper end of each tube is fixed an arm g, extending at right angles therefrom and provided at their outer ends with carbon-holders g', which hold the carbon-holders in a line parallel to the tubes c and c. Between the two solenoids is freely mounted a Winding-drum h, having two Winding surfaces, the circumference of one of which is twice that of the other. To the smaller spool is attached one end of a cord 1T, which thence leads over a guide-pulley t" and finally tothe upper end of the tube e, to which it is iirmly attached. To the larger spool of the winding-drum is attached one end of a cord j, which thence leads directly' to the lower end of tube c, to which it is firmly attached. Both cordst' andj are attached to the same side of the winding-drum, so that the pull of the cords upon the drum caused by the Weight of each tube and its attachments will be in opposite directions, and inasmuch as the tube which is attached to the small spool is about one-half the size, and consequently of about one-half the weight of the tube attached to the large spool, they will balance each other and tend to maintain the radiant point of the lamp at a tixed position. These two forces acting upon the drum, however, will be so nearly balanced that the slightest excess of pull on one side will be very quickly felt. The lamp will be designed so that any variation of current will cause the core of the main solenoid a to move twice the distance of that of the solenoid b.

In the operation of the lamp, the current being turned on, the arc is tirst formed by the main solenoid, which lifts the upper carbon. The adjustment of the lamp will be such that when the arc is of the normal length the pull of the shunt-solenoid plus the force of gravity will exactly balance the pull of the main solenoid. When by the consumption of the carbons the resistance of the arc increases, the shuntmagnet will correspondingly be increased in strength, while the main magnet will lose its force. The result will be that the upper carbon will drop at twice the speed IOO rio

.est disturbance of the magnetic balance,

while being substantially free from extraneous or concomitant vibrations.

Having thus described my invention, I claim- In an arc lamp, a main solenoid and a positive carbon holder, the core ot the solenoid being positively attached to the holder, in

combination with a shunt solenoid and nega# tive carbon holder, the core ot' the solenoid being positively attached to the holder, and a winding drum having two different sized spools over which two cords respectively pass, one cord being connected with the core of one solenoid While the other is connected with the `core of the other solenoid, the cores of both solenoids heilig acted upon constantly by a force such as gravity and the arrangement being such that'theforces thus acting balance each other, substantially as described.

In testimony whereof I subscribe my signature in presence of two witnesses.

RICHARD Il. CUNNINGHAM. Witnesses:

FRANK S. Oene, WM. A. Rossmann. 

